MGC018 Versus Androgen Receptor Axis-targeted Therapy in Participants With Metastatic Castration Resistant Prostate Cancer

Inclusion Criteria:

Histologically confirmed adenocarcinoma of the prostate without evidence of neuroendocrine differentiation, signet cell, or small cell features.
Participants must have ≥ 1 metastatic lesion that is present on magnetic resonance imaging (MRI), computed tomography (CT), or bone scan obtained ≤ 28 days prior to initiation of study treatment.
Tumor progression at study entry documented by PSA or imaging per PCWG3 criteria
Received 1 prior ARAT for metastatic prostate cancer (mPC) with lack of progression for at least 12 months
Received 1 prior taxane-containing regimen for mPC.
May have received up to 1 prior cabazitaxel regiment for mPC.
Availability of archival or formalin-fixed paraffin-embedded (FFPE) tumor tissue sample for participants with metastasis to internal organs
Acceptable physical condition and laboratory values.

Exclusion Criteria:

Any underlying medical or psychiatric condition impairing participant's ability to receive, tolerate, or comply with the planned treatment or study procedures.
Prior chemotherapy other than docetaxel or cabazitaxel. Prior immunotherapy and radiopharmaceutical therapy is allowed.
Known history of documented BRCA or ATM mutation (germline or somatic). Participants with known BRCA or ATM mutation who had disease progression or unacceptable toxicity on a PARP inhibitor are eligible.
Another hematologic or solid tumor ≥ stage 1 malignancy that completed surgery, last dose of radiotherapy, or last dose of systemic anti-cancer therapy ≤ 2 years from first dose of study treatment. Participants who had curative therapy for non-melanomatous skin cancer or for localized malignancy are eligible.
Untreated, symptomatic central nervous system (CNS) metastasis.
Prior treatment with any B7-H3 targeted agent for cancer,
Contradictions to the use of corticosteroid treatment
Prior stem cell, tissue, or solid organ transplant.